WDM system that uses nonlinear temporal gratings

• US 6,404,526 B2
• Filed: 03/08/2001
• Issued: 06/11/2002
• Est. Priority Date: 08/03/2000
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Hakimi, Farhad, Hakimi, Hosain
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): SINGH, DALZID E
• Application Number:
  US09/802,751
• Publication Number:
  US 20020015206A1
• Time in Patent Office: 460 Days
• Field of Search: 359/111, 359/122, 359/126, 359/154, 359/161, 359/169, 359/173
• US Class Current: 398/158
• CPC Class Codes: H04B 10/25077 using soliton propagation

Abstract

A method of generating a signal including: generating a first sequence of coherent optical pulses which are sufficiently close in spacing so as to overlap and interfere upon traveling a predetermined length down an optical fiber to form a first interference pattern with a first central lobe having a characteristic wavelength, wherein the energy of the pulses of the first sequence of pulses is within the non-linear regime of the optical fiber; manipulating the first sequence of optical pulses; in a similar manner generating a second sequence of coherent optical pulses; manipulating the second sequence of optical pulses; and introducing both the first and second manipulated sequences of pulses into the optical fiber, wherein the manipulating of the pulses of the first and the second sequence of pulses shifts the characteristic wavelengths of the first and second central lobes, respectively, to first and second transmission signal wavelengths.

Claims

1. A method of generating a signal for transmission down an optical fiber characterized by dispersion and a non-linear regime of operation, said method comprising:

generating a first sequence of coherent optical pulses each of which has an associated energy, wherein the pulses in the first sequence of optical pulses are sufficiently close in spacing so that upon traveling a predetermined length down the optical fiber, the pulses of the first sequence of pulses will overlap and interfere to form a first interference pattern with a first central lobe having a characteristic wavelength, and wherein the associated energy of at least one of the pulses of the first sequence of pulses is within the non-linear regime of the optical fiber;

manipulating the pulses of the first sequence of optical pulses to generate a first manipulated sequence of pulses;

generating a second sequence of coherent optical pulses each of which has an associated energy, wherein the pulses in the second sequence of optical pulses are sufficiently close in spacing so that upon traveling a predetermined length down the optical fiber, the pulses of the second sequence of pulses will overlap and interfere to form a second interference pattern with a second central lobe having a characteristic wavelength, and wherein the associated energy of at least one of the pulses of the second sequence of pulses is within the non-linear regime of the optical fiber;

manipulating the pulses of the second sequence of optical pulses to generate a second manipulated sequence of pulses; and

introducing both the first manipulated sequence of pulses and the second manipulated sequence of pulses into said optical fiber,

wherein the manipulating of the pulses of the first and the second sequence of pulses shifts the characteristic wavelengths of the first and second central lobes, respectively, to first and second transmission signal wavelengths.

2. The method of claim 1 wherein each of the pulses of said first sequence of pulses has energy that is within the non-linear regime of the optical fiber.

3. The method of claim 2 wherein each of the pulses of said second sequence of pulses has energy that is within the non-linear regime of the optical fiber.

4. The method of claim 1 wherein the step of manipulating the pulses of the first sequence of optical pulses comprises changing at least one of amplitude, phase, and timing of the pulses of the first sequence of pulses relative to each other.

5. The method of claim 4 wherein the step of manipulating the pulses of the second sequence of optical pulses comprises changing at least one of amplitude, phase, and timing of the pulses of the second sequence of pulses relative to each other.

6. The method of claim 1 wherein the first sequence of pulses includes only two pulses.

7. The method of claim 6 wherein the second sequence of pulses includes only two pulses.

8. The method of claim 1 wherein generating said first sequence of coherent optical pulses comprises delivering a first coherent laser beam at a first predetermined wavelength and producing said first sequence of pulses from the first coherent laser beam.

9. The method of claim 8 wherein generating said second sequence of coherent optical pulses comprises delivering a second coherent laser beam at the first predetermined wavelength and producing said second sequence of pulses from the second coherent laser beam.

10. The method of claim 1 further comprising encoding first data onto the first sequence of pulses before manipulating the pulses of the first sequence of pulses.

11. The method of claim 10 further comprising encoding second data onto the second sequence of pulses before manipulating the pulses of the second sequence of pulses.

12. The method of claim 1 wherein introducing both the first manipulated sequence of pulses and the second manipulated sequence of pulses into said optical fiber comprises passing both the first manipulated sequence of pulses and the second manipulated sequence of pulses through a wavelength multiplexer.

13. The method of claim 1 wherein generating said first sequence of optical pulses comprises:

supplying a first continuous single coherent wave laser beam at a first preselected wavelength; and

chopping the first continuous wave laser beam to produce the first sequence of optical pulses.

14. The method of claim 13 wherein generating said second sequence of optical pulses comprises:

supplying a second continuous single coherent wave laser beam at a second preselected wavelength; and

chopping the second continuous wave laser beam to produce the second sequence of optical pulses.

15. The method of claim 14 wherein the first and second preselected wavelengths are the same.

16. The method of claim 1 wherein generating said first sequence of optical pulses comprises:

supplying a first single coherent optical pulse at a first preselected wavelength; and

producing the first sequence of optical pulses from the first single coherent optical pulse.

17. The method of claim 16 wherein generating said second sequence of optical pulses comprises:

supplying a second single coherent optical pulse at a second preselected wavelength; and

producing the second sequence of optical pulses from the second single coherent optical pulse.

18. The method of claim 17 wherein the first and second preselected wavelengths are the same.

19. An apparatus for sending optical signals down an optical fiber characterized by dispersion and a non-linear regime of operation, said apparatus comprising:

a first optical signal source which during operation generates a first sequence of coherent optical pulses each of which has an associated energy, wherein the pulses in the first sequence of optical pulses are sufficiently close in spacing so that upon traveling a predetermined length down the optical fiber, the pulses of the first sequence of pulses will overlap and interfere to form a first interference pattern with a first central lobe having a characteristic wavelength, and wherein the associated energy of at least one of the pulses of the first sequence of pulses is within the non-linear regime of the optical fiber;

a frequency shifter which during operation manipulates the pulses of the first sequence of optical pulses to generate a first manipulated sequence of pulses;

a second optical signal source which during operation generates a second sequence of coherent optical pulses each of which has an associated energy, wherein the pulses in the second sequence of optical pulses are sufficiently close in spacing so that upon traveling a predetermined length down the optical fiber, the pulses of the second sequence of pulses will overlap and interfere to form a second interference pattern with a second central lobe having a characteristic wavelength, and wherein the associated energy of at least one of the pulses of the second sequence of pulses is within the non-linear regime of the optical fiber;

a second frequency shifter which during operation manipulates the pulses of the second sequence of optical pulses to generate a second manipulated sequence of pulses; and

a wavelength division multiplexer system which during operation receives both the first manipulated sequence of pulses and the second manipulated sequence of pulses and introduces them into said optical fiber, wherein the first and second frequency shifters shift the characteristic wavelengths of the first and second central lobes, respectively, to first and second transmission signal wavelengths.